Three-dimensional imaging of the plasma parameters of a moving cusp aurora

Taguchi, S.; Hosokawa, K.; Ogawa, Y.

doi:10.1016/j.jastp.2015.08.012

Cited by 3 publications

(13 citation statements)

References 37 publications

(34 reference statements)

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“…The aurora structure analyzed in Taguchi et al . [], however, was not a completely isolated auroral event as explicitly stated in the paper. The data obtained after time 7, as shown in their Figure 8a, reflect variations associated with a different moving auroral structure that appeared immediately after the auroral structure examined in that paper.…”

Section: Introductionmentioning

confidence: 76%

“…By examination of a moving cusp aurora structure with a typical horizontal scale of roughly 100 km × 200 km, Taguchi et al . [] indicated that the maximum 630.0 nm intensity of the auroral structure occurs immediately behind the moving F region‐enhanced electron density volume created by precipitating electrons. This indication is based on the delay of the auroral intensity peak of approximately 40 s from the peak of the electron density [ Taguchi et al ., , Figures 8a and 8b].…”

Section: Introductionmentioning

confidence: 99%

“…[] indicated that the maximum 630.0 nm intensity of the auroral structure occurs immediately behind the moving F region‐enhanced electron density volume created by precipitating electrons. This indication is based on the delay of the auroral intensity peak of approximately 40 s from the peak of the electron density [ Taguchi et al ., , Figures 8a and 8b]. This delay time is consistent with the lifetime of O( 1 D ), which suggests that the spatial relationship obtained by Taguchi et al .…”

Section: Introductionmentioning

confidence: 99%

“…This delay time is consistent with the lifetime of O( 1 D ), which suggests that the spatial relationship obtained by Taguchi et al . [], such that the maximum 630.0 nm intensity in the cusp auroral structure is located immediately behind the enhanced electron density volume created by the precipitating electrons, is related to the relatively long lifetime of O( 1 D ). The aurora structure analyzed in Taguchi et al .…”

Section: Introductionmentioning

confidence: 99%

“…In the present paper, we examine multiple events of isolated moving cusp aurora by using aurora image data having higher time resolution than those used in Taguchi et al . []. Moreover, we investigate plasma data from the European Incoherent Scatter (EISCAT) Svalbard radar (ESR), in which the beam passes through the moving auroral structure.…”

Section: Introductionmentioning

confidence: 99%

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Horizontal profile of a moving red line cusp aurora

et al. 2017

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Auroral emission at a wavelength of 630.0 nm (red line) has a long radiative time. In this study, we show how this long radiative time controls the horizontal extent of a moving mesoscale aurora, which is typical of the cusp. Using high time resolution (4 s) observations by an all‐sky imager at Longyearbyen, Svalbard, and observations by the European Incoherent Scatter Svalbard Radar (ESR), we examined the auroral emission enhancements obtained in the cusp during an interval of southward interplanetary magnetic field on 27 November 2011. Simultaneous observations from the all‐sky imager and the ESR clearly show the manner in which auroral emission regions passed through the radar's field of view. When the front edge of the moving auroral structure intersected the radar's field of view, the ESR electron temperature was enhanced. A few minutes later, the ESR electron temperature dropped to the background level, indicating that the mesoscale electron precipitation region shifted away from the radar's field of view. At that time, the auroral emission in the radar's field of view decreased but still had adequate intensities. These results provide evidence demonstrating that moving cusp auroral emission occurs behind the electron precipitation region as well as inside that region. We interpreted this feature semiquantitatively by using the equation of continuity of the density of the excited atomic oxygen. Our model indicates that the maximum intensity in the moving auroral structure occurs at a point along the trailing edge of the electron precipitation region and that the velocity of that region is important for determining how the 630.0 nm aurora emissions extend horizontally.

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Horizontal profile of a moving red line cusp aurora

et al. 2017

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Plasma Flow in the North‐South Aligned Discrete Aurora Equatorward of the Cusp

2019

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On the equatorward side of the dayside cusp there often appear diffuse auroras. In this paper, we report north-south aligned discrete aurora events and show the spatial relationships between the auroras and the plasma flow. Several events of the north-south aligned discrete auroral structures were identified using an all-sky imager at Longyearbyen, Svalbard, during the recovery of a moderately disturbed period on 8 December 2013. During a brief interval of the moderately disturbed period, the cusp shifted to higher latitudes; as a result, the field-aligned beam of the EISCAT Svalbard Radar (ESR) passed through the northern portion of the north-south aligned auroral structures. Simultaneous observations from the all-sky imager and ESR reveal that enhancements in ion temperature (caused by fast ion flow) occurred near the eastward and westward boundaries of the north-south aligned auroral structures. However, within the region of the most enhanced aurora, the ion temperature enhancements were moderately suppressed. These features indicate that the ion flow slows down in the region of electron precipitation responsible for north-south aligned auroral structures. We can quantitatively interpret the slowdown of the flow as the reduction of the electric field due to the polarization effect in the north-south aligned region of the increased Pedersen conductivity. It thus appears that the magnetospheric source of the north-south aligned discrete auroras is a limited area embedded in the region of plasma flow toward the dayside magnetopause.

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Cusp Dynamics and Polar Cap Patch Formation Associated With a Small IMF Southward Turning

et al. 2021

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The cusp is one of the most dynamic regions in the polar ionosphere. The cusp is located near noon just poleward of the open and closed magnetic field lines of the dayside magnetosphere-ionosphere system, and a variety of energy input processes from the magnetosheath and magnetopause characterize the cusp. Precipitation in the cusp is dominated by soft electrons and energetic protons, and impact ionization and precipitation heating primarily occur in the F-region ionosphere and thermosphere (Hardy et al., 1985;Skjaeveland et al., 2017). The cusp is located at the dayside convection throat, where fast flows transport plasma from closed to open field lines (Moen et al., 2001;Sandholt et al., 2003) and increases Joule heating (Shi et al., 2017). The heating in the cusp increases plasma upflows and thermospheric density (Carlson et al., 2012;Ogawa et al., 2009). In addition to the large-scale quasi-steady convection, pulsed flows propagate poleward in association with localized field-aligned currents. The footprint of the upward FACs is illuminated as discrete auroral arcs, and it is referred to as poleward moving auroral forms (PMAFs) (Oksavik et al., 2004). This transient system is characterized as a flow channel and a wedge-like current system.An important consequence of the cusp dynamics is formation of polar cap patches. During a large southward IMF, the open-closed boundary moves equatorward and photoionized plasma from the sunlit ionosphere becomes an important source of polar cap patches (

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Three-dimensional imaging of the plasma parameters of a moving cusp aurora

Abstract: Highlights:-3D images of plasma parameters in a moving aurora from IS radar and all-sky imager -Spatial relations are found between the cusp aurora, elevated Ti, and enhanced Ne -The relationships are explained by the presence of a moving twin-convection cell

Cited by 3 publications

References 37 publications

Horizontal profile of a moving red line cusp aurora

Horizontal profile of a moving red line cusp aurora

Plasma Flow in the North‐South Aligned Discrete Aurora Equatorward of the Cusp

Cusp Dynamics and Polar Cap Patch Formation Associated With a Small IMF Southward Turning

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